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  • Writer's pictureHolly Gage

Fire-in-Place Cultured Opals Find New Compatibility With Base Metal Clays and Aussie Metal Clay

Updated: May 22, 2023

I have three guests for today’s blog commenting on the versatility of the New Healing Phoenix Lapidary Fire-in-Place Opals. With great success, eight clays were tested. Michael Galvin reports his experience working with various Base Metal Clays and Cultured Opals. In contrast, Jade Reed walks us through her firing schedule and experiences with Aussie Sterling Metal Clay 960 and the Fire-in-Place Opals. Lastly, Ann Adkins tested another Aussie Metal Clay, a beautiful Gold Bronze. Hold onto your hats; their results are pretty impressive.

At the bottom of this article is a chart summarizing the firing schedules of all the clays tested, along with a resource section of the clays and firing mediums used.


Before we dive in, let's briefly recap the clays that have been tested so far. Below are the Clays, times, temperatures, and support/insulation media. See "How to Fire in Place Healing Phoenix Cultured Opals" for in-depth details on firing Fire-in-Place Cultured Opals.


Black Fire-in-Place Cultured Opal
Black Fire-in-Place Cultured Opal

Michael Galvin’s

Base Metal Clays Test

The following is a list of the Base Metal Clays, times, and temperatures I have tested with the Black Fire in Place Opals, both cabs and faceted. I have not tested any of the other flavors at this time.

All the clays were fired with the burnout stage ON a 1” inch bed of carbon, then covered with ¾” inch minimum of carbon for the sintering stage. This is not necessarily the manufacturers’ recommended method, but it is how I fire all base metals, as I believe single-stage firing is not effective.

I set a stone in a test piece to go along for the ride while doing something else in that clay, then stripped it back out to reuse. This was only done in the Bronze clays, which saw a maximum of 1,540°F, and I have one 6mm stone that has seen 1,500°F three times for a total of 5 hours at sinter temperature with no degradation.

I also have a ring with (2) 6mm stones that has seen two cycles at 1,675°F in Copper for a total of 6 hours with no ill effects. I have done PMC OneFire at the recommended schedule open shelf. If there was an issue, it’s noted, but there was only one. Here is the list so far:

Art Clay Bronze

Burnout 720°F for 30 minutes, Sinter 1,500°F for 1.5 hours.

Five Star Copper

Burnout 750°F for 35 minutes, Sinter 1,650°F for 2 hours.

Goldie Copper

Burnout 1,050°F for 45 minutes, Sinter 1,650°F for 3 hours. This worked fine.

Burnout 1,050°F for 45 minutes, Sinter 1,760°F for 2.5 hours. This did NOT work and was the only issue I’ve had. The color was fine, and the stone stayed in one piece, but the surface was seriously pitted and unacceptable. I believe it is strictly temperature related. It was fine at a lower temp.

Black Fire-in-Place Cultured Opal
Black Fire-in-Place Cultured Opal

Goldie Gold Bronze

Burnout 700°F 30 minutes, Sinter 1,520°F 1.25 hours.

Metal Adventures BronzClay (not fast fire)

Burnout 750°F 30 minutes, Sinter 1,500°F 1.5 hours.

Metal Adventures White CopprClay

Co-Fired with both Five Star Copper & Goldie Copper

Burnout 700°F for 45 minutes, Sinter 1,650°F for 3 hours. This is a significantly lower temperature than recommended for White Copper (slow ramp in carbon, then 1,850°F for 2 hours). It sintered just fine at the lower temperature for an extended 3 hours. One piece saw this schedule twice & the Opals were fine.

I haven’t seen any reaction with a specific clay or Base Metal. The only issue I’ve experienced was temperature related, and that clay worked at a lower temp.

Michael Galvin

I am a 63-year-old Metal Clay hobbyist who has been exploring the medium for 8+ years, but my roots in Jewelry fabrication by more traditional methods go back over 50 years, with experience in lost wax, sand casting, and traditional metalsmithing. My work in Metal Clay is 75% base metals and 25% Silver. I am a degreed Composite Material Development Engineer with an M.B.A. and extensive experience in Aerospace Development & Heavy Automotive Manufacturing Operations. “Most of my Metal Clay work is Engineered, not designed.” Michael can be reached on Facebook at:


Healing Phoenix Lapidary
Healing Phoenix Lapidary

At Healing Phoenix Lapidary:

  • Shop for Fire-in-Place Cultured Opals. Find more information on compatible Metal Clays and firing information.

  • How to handle Fire-in-Place Opals.

  • General information.


Jade Reed Aussie Metal Clay 960 (AMC) Tests

In September 2022, I read the “Fire in Place Opals” blog from Holly Gage and thought that this was something I must try. I quickly placed an order from the United States and waited impatiently for the Cultured Opals to arrive in Western Australia. When I received my order, I quickly began creating to see how good they really were!! l just love, love, love them, and have since placed a second order.

White Iridesence Fire-in-Place Cultured Opal
White Iridesence Fire-in-Place Cultured Opal

Aussie Metal Clay 960 Sterling Silver

The first piece I created using the White Iridescence Cultured Opal was a heart pendant in Aussie Metal Clay 960 Sterling Silver.

  • I fired it in my paragon kiln ramp 800°C (1472°F)

  • Target temperature is 910°C (1670°F)

  • Hold for 1 hour and 45 minutes, placed face up buried in Kim’s No Fuss Fire Medium (KNFF). This came out perfect.

  • I place a bed of about 2 cm (.78” or roughly 3/4”) in the bottom of the crucible and place the first layer to be fired.

  • I then gently spooned a nice thick coating of KNFF over and into the pieces (with rings, this helps keep the shape) to about 2 cm (.78” or roughly 3/4”). If the crucible is large enough and I have made enough pieces, I place one more layer and then cover it with another 2 cm (.78” or roughly 3/4”) above the top of the highest point. Layering definitely adds time to the firing. I always add a test strip to the middle of the crucible in a layered firing.

Bermuda Ocean Fire-in-Place Cultured Opal
Bermuda Ocean Fire-in-Place Cultured Opal

I prefer to use the Aussie clays and always fire in Kim's No Fuss Fire Medium, which helps create a stronger sinter and keeps the shape of delicate items.

I temped fired (9) pieces simultaneously; the crucible was full, and they were layered in the No Fuss Medium. The schedule was the same 800°C (1472°F) ramp / 910°C (1670°F), but this time I fired for 3 hours. Again the opals were perfect, with the Bermuda Ocean Fire-in-Place Cultured Opal being my favorite.


Editors note: Poor Jade, I had her continue to test the Cultured Fire-in-Place Opals because 900°C / 1650°F is the top recommended firing schedule. Yet her tests throughout her experiments with Aussie Sterling Silver 960 have proven successful regardless of the higher temperatures she used. A bit of a warning is in order if you use a higher schedule, as I've experienced cracking or hazing, but I never used KNFF medium. ~ Holly

I have since agreed to test a few more firings with the cultured opals; I fired 4 more opals, 2 in KNFF & 1 in vermiculite, at a ramp of 800°C (1472°F) to a hold temp of 910°C (1670°F) for 2 hours.

In a separate firing, I fired 1 in KNFF at a ramp of 800°C (1472°F) to a hold temp of 910°C (1670°F) for 1 hour.

Three of these opals I have put in for a 2nd firing at a ramp of 800°C (1472°F) to a temp of 910°C (1670°F) for 45 mins. They have all come out perfectly, although I did manage to break one earring, so I have decided to push the limit even further, and I have repaired the earring and have now completed a 3rd firing and fired the pair at a ramp of 900°C (1652°F)to a hold of 918°C (1684°F) for 20 mins., again they are fine, (I have used these temperatures just to see how far I can push the limit)

I want to add a note that my kiln fires 3ºC hotter than the readout on the kiln. The fact is every kiln is different, and you need to get to know your kiln.


My name is Jade Reed, and I live in outback Western Australia and have been learning, creating, and sharing my craft for over 30 years. In 2017, I discovered Metal Clay and love to use Aussie Metal Clay silvers for my creative pieces, and like to include locally sourced natural gold nuggets and, now, Cultured Opals.

Find her at Desert Designs:

All this information should give you even more motivation to enter the...
The contest is held on the Metal Clay and Mixed Media forum.

Ann Adkins Aussie Metal Clay Gold Bronze (AMC) Tests

Christopher and Holly Gage have brought beautiful Fire-in-Place (FIP) Opals to Metal Clay artists for use in jewelry and Metal Clay art. Feedback has been wonderful for use in different metal clays, and I was interested in seeing the results when using my favorite Metal Clay, Aussie Metal Clay (AMC) Gold Bronze. AMC Gold Bronze can be fired using three different methods — traditional carbon, Kim’s No Fuss Fire (KNFF), and Kim’s 1 Stage Rapid Fire (1SRF). I chose the KNFF method because Holly had great success in firing in vermiculite, and the KNFF method utilizes a firing powder that gives great support and protection during firing.


I made a pair of AMC Gold Bronze earrings with the 6mm Black FIP Opals and used my Cricut Explore 2 to cut out and texture the baseplate of the piece. I then textured and attached a Moroccan flower center to give the earrings some dimension and contrast. You have to add some dots. I used AMC Clay Stay to secure the clay pieces and then used my hand drills and 6mm setting burr to make a setting for my Opals. I put an azure — a hole behind the stone when firing a faceted stone, to give the stone some room to move in the backplate during the shrinkage of the piece (unless I forget!). I then set the stone and put a decorative bezel cover to finish the piece. Then let everything dry thoroughly.


After some gentle sanding and wet refinement, the earrings were ready for the kiln. KNFF results in low shrinkage with AMC Gold Bronze, about 8% in my kiln.

  • KNFF powder is placed at the bottom of the firing pan. I used 20mm so that my piece is not touching the bottom of the pan.

  • The pan is placed in the kiln for the burnout phase at Ramp 1526°F to 752°F and hold for 30 minutes. The pieces are the classic dark color after burnout.

  • The pan was taken out to cool slightly, and the kiln was set for the sintering stage at Full Ramp to 1470°F for 2 hours.

  • When the firing pan was cooled sufficiently to touch, the pieces were covered with 30 mm activated coconut carbon and placed in the kiln for sintering.

After Firing

The Black Opals were clear, without hazing, the piece had not deformed, shrinkage was 8%, and the test strip showed a good sinter with no cracking. The earrings were then placed in the magnetic tumbler for 15 minutes to burnish up before attaching the earring posts.


Sterling silver earring posts were soldered on with easy solder carefully because I have

melted Bronze pieces before. They do not take the heat of the soldering torch as kindly as Sterling Silver because of the lower melting point. Once the posts are twisted and hardened in place and firm, they go back in the tumbler for more burnishing and to make sure the posts are attached well.

Black Fire-in-Place Cultured Opal
Black Fire-in-Place Cultured Opal


Polishing was done with the JoolTool and 3M Radial Brush Discs, the Scratch Erasers, Polish, Pink Buff, and then a quick cleaning with a soft brush. The Opals turned out to be a beautiful centerpiece for the earrings, and the contrast of the fiery red and green flashes with the bright gold is lovely.

Ann Adkins started in metalsmithing and found Metal Clay during the 2020 lockdown. She lives and works in South Louisiana and is a Level I certified teacher for Aussie Metal Clays (AMC) in silver and base clays. She is most inspired by gemstones, French art, her faith, and other amazing Metal Clay artists.


Editors note: Some have tumbled the Cultured Opals with no problem, as Ann has. However, I treat these Fire-in-Place Opals like Natural Opals even though Natural Opals are 5 and these Fire-in-Place Opals are 6.5 on the Mohs hardness scale. Putting Grafix Incredible White Mask Liquid Frisket on the Opals will ensure their safety in the tumbler. (See the Reference section for a link) ~ Holly


Resources Healing Phoenix Lapidary Fire in Place Opals -

Art Clay Metal Clay -

Five Star Metal Clay - Goldie Metal Clay -

Metal Clay Adventures - Rio Grande -

Aussie Metal Clays, KNFF, Stay Clay -

Grafix Incredible White Mask Liquid Frisket - Dick Blick -

Fire-in-Place Opal Firing Chart by Healing Phoenix Lapidary
Fire-in-Place Opal Firing Chart by Healing Phoenix Lapidary


Healing Pheonix Lapidary has beautifully Cut Artisan Opals Every Friday. Join the fun at this Facebook Auction!


May 25, 2023

Newbie question about torch firing, do I still need to deep bury it in vermiculite?

Holly Gage
Holly Gage
May 25, 2023
Replying to

Hi unknown newbie, This Cultured Opal can be fired directly in a Torch on a bed of vermiculite. Stone facing down, culet or pointed side facing up. Complete firing information can be found here. I'd love to see what you create! ~ Holly

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